[doc] debug: fix import (#19042)

correct the import statement

Author: stas00

docs/source/en/debugging.mdx

@@ -77,7 +77,7 @@ to the normal command line arguments, or pass `debug="underflow_overflow"` when
 If you're using your own training loop or another Trainer you can accomplish the same with:
 
 ```python
-from .debug_utils import DebugUnderflowOverflow
+from transformers.debug_utils import DebugUnderflowOverflow
 
 debug_overflow = DebugUnderflowOverflow(model)
 ```
@@ -271,7 +271,7 @@ Additionally, if you're instantiating the debugger in your own code, you can adj
 its default, e.g.:
 
 ```python
-from .debug_utils import DebugUnderflowOverflow
+from transformers.debug_utils import DebugUnderflowOverflow
 
 debug_overflow = DebugUnderflowOverflow(model, max_frames_to_save=100)
 ```